With the continuous development of science and technology, photovoltaic power generation systems are developed rapidly. Generally, in a current photovoltaic power generation system, multiple photovoltaic modules are connected in series to form a photovoltaic string, and photovoltaic strings are connected in parallel to form a photovoltaic array. An inverter converts a direct current (DC) into an alternating current (AC) by performing maximum power point tracking (MPPT) control on the photovoltaic string or the photovoltaic array, and transmits the AC to the power grid.
For conventional photovoltaic power generation systems, a centralized photovoltaic power generation system usually performs MPPT on only one path, and both a string-type photovoltaic power generation system and a distributed photovoltaic power generation system perform MPPT on multiple paths. However, series mismatch and parallel mismatch among modules may be caused due to factors such as shadow occlusion and differences between module parameters, thereby resulting in a loss in a power generation capacity.
At present, in order to solve the series mismatch and parallel mismatch among the photovoltaic modules, each of the photovoltaic modules is generally provided with an optimizer having a module-level MPPT function. As shown in FIG. 1, multiple optimizers are connected in series to form an optimizer set, and multiple optimizer sets are connected in parallel to a DC input terminal of a grid-connected inverter.
However, it is found by the inventor that with the optimizers having such structure, in order to ensure that the inverter operates in an optimal operating range, the DC bus voltage of the grid-connected inverter is usually controlled to be a constant value. In a case where there is a great difference between maximum powers of photovoltaic panels in the same optimizer set (in a case where the photovoltaic panels are uniformly shielded by leaves, dark clouds and the like), the maximum power generation capacity of the system cannot be achieved with the conventional solution.
Therefore, a technical issue to be solved urgently by those skilled in the art is to provide a photovoltaic power generation system, such that the maximum power generation capacity of the photovoltaic power generation system can be achieved.